1. Field of the Invention
The present invention relates to an optical disk in which main formation is recorded by concave/convex recording marks as well as sub information is recorded by changing the reflection coefficient of a reflection film provided on a region where the concave/convex recording marks are formed, and an optical disk reproducing device for reproducing the optical disk.
2. Description of the Background Art
Recently, optical disks have been widely used as a content distribution medium for movies, music, games, and the like. Also, because of the recent dissemination of high-speed networks, distribution of content information via a network has become active.
In obtaining the content information via the network, a usage fee of the content information will be billed. A safe billing is done currently by utilizing a credit card or card type electronic money. Therefore, users who do not have credit cards or electronic money are not able to use such a system.
In view of the above, such inventions are disclosed that users who do not have credit cards can use an electronic payment via a network (for example, see Japanese Unexamined Patent Publication No. 2002-324200).
According to the above described technique, a user initially purchases an optical disk or a prepaid card assigned with a specific media identification number (SC-ID). Then, a client terminal device reads out the media identification number and identification information (MC-ID) specified for every memory card. A client ID specified for every client device is sent to a server together with the media identification number. The server stores a prepaid money amount corresponding to the SC-ID in association with the MC-ID and the client ID. The server, subsequently, specifies the user to be served based on the MC-ID and the client ID upon providing a service, and takes a billing procedure to a prepaid money amount of the user for a money amount consistent with the service to be provided, thereby providing the service. Therefore, a service requiring billing can be provided to a user without a credit card.
However, the above described conventional technique necessitates a network connection with a server in order to perform the billing procedure. As such, the above-described conventional technique cannot be used in such a situation that a server cannot be connected to a network. For example, in the case where every view of the content information having been stored in a memory card is required to be billed, if the client terminal device cannot be connected to the network, the user cannot use the content information.
Also, the above-described conventional technique requires an optical disk or a prepaid card storing money amount information in addition to a memory card.
Further, in the case where the money amount information is recorded in the optical disk by a normal recording method, there is a problem of illegal copying of the money amount information.
Still further, since the money amount information is registered at the server side upon using it, past-used optical disk or prepaid card information should be managed semipermanently. Without such management of information, the spent optical disk or prepaid card may be used illegally.